This invention relates to collapsible liquid storage tanks, and in particular, it relates to a frameless collapsible liquid storage tank having a closeable opening at the top of the tank.
It is often desirable to have a container or storage tank capable of holding a liquid such that when there is no liquid in the container it may be collapsed or folded for ease of transportation and storage. Collapsible liquid containers have been around for some time and encompass a variety of designs. Examples of early collapsible containers are shown in U.S. Pat. No. 2,664,131 to Miller and U.S. Pat. No. 2,754,869 to Bartels, herein incorporated by reference. Miller and Bartels disclose collapsible buckets or pails having sidewalls and bottoms of a flexible moisture impervious material. Both Miller and Bartels also include open tops and rigid reinforcing rings at the upper and lower ends of the sidewalls. The reinforcing rings aid in the stability of the container and assist in maintaining the container shape while being filled with a liquid, the hydrostatic pressure of the liquid aids in maintaining the containers in an upright non-collapsed position. It is also believed the frusto-conical shape shown by Bartels wherein the bottom of the container is larger than the top aids in maintaining the shape and stability of the tank because the liquid contained therein employs an upward pressure on the sidewall and reduces the effective horizontal vector of the hydrostatic pressure against the sidewall.
Another form of a collapsible container is found in U.S. Pat. No. 5,622,277 to Van Giezen et al., herein incorporated by reference. The collapsible container in Van Giezen has a collapsible sac which is supported by a rigid frame. The frame can be folded or disassembled for transportation and/or storage. A drawback, however, to a collapsible tank with rigid support frames is that the support frames even in the folded or disassembled state still occupy a substantial space and significantly add on the bulk and weight of the container.
Another type of collapsible liquid storage tanker container is the tube or pillow type such as is found in U.S. Pat. No. 4,573,508 to Knaus; U.S. Pat. No. 4,597,425 to Tally; and U.S. Pat. No. 5,499,743 to Blumenkron, all herein incorporated by reference. The containers found in Knaus, Tally, and Blumenkron are relatively light weight and compactable when not filled with a liquid as they have no frame or rigid support rings. These containers are formed of a flexible fiber reinforced elastomeric material and have inlets or nozzles at the sides for filling and draining purposes. One of the benefits of tube or pillow containers is that they provide a good environmental seal to keep contaminants from either entering or leaving the tank. A drawback of this type of container is that the size of the valves or nozzles are relatively small and do not provide for quickly filling or draining of the tank. In addition, as the interior of the tanks are sealed, except for the nozzle or valve, cleaning the inside of the tanks is difficult, and there is no access for wiping down the interior of the tank during cleaning.
Another example of a collapsible tank is found in U.S. Pat. No. 5,964,369 to Greene, et al, herein incorporated by reference. The container disclosed by Greene is somewhat similar to the tube or pillow containers discussed above in that it has a valve for filling and draining it, and wherein the valve is supported by a rigid ring. The patent to the Greene, though, has the valve located at the top of the tank as opposed to the side. However, the container disclosed by Greene still has the same drawbacks as the tube Containers regarding ease of filling, draining and cleaning.
An alternative to the tube tanks discussed above, is open top water tanks such as disclosed in U.S. Pat. No. 5,429,437 to Shaw et al, and U.S. Pat. No. 6,021,915 to Shimozono et al, herein incorporated by reference. These containers are somewhat similar to the pails disclosed by Miller and Bartels except on a larger scale. As these tanks have an open top, they provide the ease for filling, draining, and cleaning not found in the tube tanks. However, these tanks have a drawback in that as the top is open, any liquid in the tank is exposed to the environment and contamination therefrom. Another drawback of these containers is that they require a stiffening or floating member at the top of the sidewall and/or one at the bottom of the sidewall. These members may be made from metal, stiff plastic, or a floating foam such as polyethylene foam. The stiffening members add bulk and weight to the tank when it is not holding a liquid and is in its collapsed state.
In order to provide a minimal environmental barrier for open top tanks, it has been known to equip the tanks with a cover that is held down by straps or ties. The drawback to this type of cover is that it still does not provide an adequate environmental seal, especially in adverse or windy conditions when the top will be subject to blowing and the ties may be torn away. Also, in order to overcome the weight and storage drawbacks of a rigid or floating ring at the upper sidewall, it has been known to provide an air inflated ring about the top sidewall. The inflatable collar allows the tank to be filled without spilling over the sides as the collar floats and rises with the liquid level. However, inflatable collars have the drawback that they require inflation devices to be carried with the container for inflation of the collar and increase the complexity and cost of the storage tank. Furthermore, the tank is rendered useless if a leak is developed in the collar.
As such, it is the object of this invention to provide a tank combining benefits of both the open top tanks discussed above plus the tube and pillow tanks without the drawbacks associated with either tank. In particular, it is an object of the invention to provide a tank that is openable from the top being easily filled and drained. It is another object of the invention to provide a tank that may be easily cleaned and wiped down on the interior of the tank and is suitable for holding potable liquids.
It is also an object of the invention to provide a frameless tank having no support frame, rigid or floating support members at either the upper or lower ends of the sidewalls thereof. It is a further object of this invention to provide a tank that can be easily filled without spillage and has no inflatable member. It is also an object of the invention that the tank be capable of being used on a surface having an incline of at least 10 degrees and being filled with a liquid without spillage.
Lastly, it is an object of the invention to provide a frameless collapsible liquid storage tank being openable at the top, yet providing an effective barrier against environmental contamination.